Highlight Dot

A highlight dot is the smallest tint in the file, usually somewhere between 3% and 10%, and it is physically fragile in ways paper printing never has to consider. At 55 lpi a 5% dot measures roughly 0.0046 inches across, about 117 microns. The open square in a 156 mesh screen is near 99 microns. So the entire highlight dot sits on one or two thread openings with almost nothing anchoring it to the mesh, which lets it undercut during exposure, rinse away in washout, or shear off after sixty impressions.

For a buyer this shows up as a portrait whose eyes lose their catchlight and whose forehead goes bald white. The glowing part of a photograph is built from highlight dots, and it is the part most likely to vanish between proof and shirt. On a memorial run of 300 we stacked shirt 8 next to shirt 240 for a final QC check, and the widow's face had flattened into a paper cutout; the 4% cheek tones were still on the film, just no longer on the mesh. We reprinted 232 pieces on our own dime and reshot the screen at 305.

Working printers set a minimum holdable dot and defend it. At 55 lpi on 230 mesh, a 4:1 mesh-to-lpi ratio, 8-10% is a realistic floor; move to 305 mesh with disciplined exposure and 6% becomes reachable. Either lift everything under the floor up to it in the RIP curve or clip it to zero on purpose, so the edge of the highlight is a decision rather than an accident. Clipping buys repeatability and costs you softness.

New printers assume a highlight dot that prints on the first shirt will print on the last. It will not. Small dots fail progressively and the run drifts lighter, so the smallest dot on your film should be one you would happily see at shirt 500.